Trademarks and trade names used herein are shown in upper case.
Sootblowers are an integral part of temperature control on combustion devices such as steam generators, furnaces and boilers. Sootblowers are cleaning devices which are used to remove deposits of soot, ash and debris from surfaces, such as furnace walls, and the surfaces of heat exchange tubes, particularly on the surfaces of tubes located within combustion devices. During operation of a combustion device, hot combustion gases from a boiler or furnace pass over the heat exchange tubes, which are generally provided in clusters of tubes, whereby the tubes absorb heat and thus heat the contents of each tube in the usual heat exchange function. Soot or ash generated from the combustion of fuel, deposit on the tubes, insulating the tubes, and making the tubes less effective as heat exchange units. Therefore, the tubes must be periodically thoroughly cleaned. Sootblowers, using air, steam or water under high pressure, literally blow deposits off surfaces and thus prevent deposits from insulating the tubes, which would reduce the exchange or transfer of heat by the tubes and adversely affect their function. Therefore, proper operation of the sootblower is essential to proper operation of a furnace or other combustion device.
Significant effort is devoted to sootblower maintenance. Many components are designed such that they can be replaced or repaired in place if they fail. Without proper maintenance, catastrophic failure of the sootblower may occur, requiring total replacement. Replacement is expensive and involves not only cost to replace the sootblower, but also freight and handling charges, installation, equipment downtime, including possible reduction of efficiency, etc. Sootblower manufacturers recommend preventative maintenance programs.
Critical to the operation of sootblowers is proper lubrication. In practice, the sootblower has a number of parts, including gears, bearings and seals, that require lubrication in order to maintain performance. Lubricants, especially in the gear box and in bearings and seals are exposed to high temperature, for example, 300° to 850° F. (150° to 454° C.) and high pressure, for example, 50 to 700 psig (345 kPa to 2413 kPa). Degradation and leaks of lubricant are frequent causes of sootblower maintenance problems, and, if not addressed, may lead to catastrophic failure.
Hydrocarbon oils, hydrocarbon-based greases, synthetic hydrocarbon oils and synthetic hydrocarbon-based greases, and mixtures thereof, are the most common lubricants utilized in sootblowers. These oils and greases degrade and/or oxidize into tars over time in the high temperature environment in which the sootblower operates, thereby causing premature sootblower failure. These oils and greases may leak or worse, form hard varnish layers, again leading to premature sootblower failure. Sootblower failure due to failure of seals, bearings, and/or gears, reduces equipment capacity, such as boiler, capacity and increases maintenance costs. Use of full-flow circulating oil baths on gear sets, gaskets and shaft surfaces has improved reliability of synthetic hydrocarbon oils and greases.
There remains a need for a method for lubricating sootblowers for longer and more reliable performance, with reduced, and even elimination of, maintenance of sootblower lubrication systems. The present invention meets these needs.